1. Field of the Invention
The present invention relates to a solar cell, and more particularly, the present invention relates to a solar cell having an improved structure.
2. Description of the Related Art
A solar cell generates electric energy using solar energy. The solar cell is eco-friendly and has an infinite energy source and a long life span. The solar cell includes a silicon solar cell and a dye-sensitized solar cell.
The silicon solar cell includes a semiconductor substrate and an emitter layer that have different conductive types to form a PN junction, a first electrode electrically connected to the emitter layer, and a second electrode electrically connected to the semiconductor substrate.
The first electrode is formed on a front surface of the semiconductor substrate and the second electrode is formed on a rear surface of the semiconductor substrate. However, in such a solar cell, since shading loss due to the first electrode is significantly large, of the order of 10%, the efficiency of the solar cell can be reduced.
In order to reduce the shading loss, a rear-electrode type solar cell, in which a first electrode is formed on a rear surface of a semiconductor substrate, has been suggested. In such a rear-electrode type solar cell, charges generated in a PN junction must move into the first electrode by a relatively large distance. Accordingly, re-coupling probability such as impurity-crystal coupling may increase and thus electrical loss may increase.
In order to prevent the electrical loss, a non-defective semiconductor substrate must be used. However, since it is substantially impossible to manufacture the non-defective semiconductor substrate, economical efficiency is low.
In the rear-electrode type solar cell, the electrical loss increases as the movement distance of the charges increases. Accordingly, in spite of reducing the shading loss, efficiency cannot be significantly improved.